This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Retinol and its metabolites participate in many physiological processes, such as growth, development, reproduction, cellular differentiation, and vision. Rats fed with retinol-free and all-trans-retinoic acid (atRA)-supplemented diet fail to reproduce. It has been shown that retinol is required no later then day 10 of gestation in order to prevent fetal resorption in the vitamin A deficient, atRA-supplemented (VAD-RAS) female rats. Metabolic studies on all trans retinol in day 10 conceptuses of vitamin A deficient, retinoic acid supplemented rats led to the isolation and identification of a novel metabolite, the isomers of 2-(hydroxymethyl)-3-methyl-5-(2'-oxopropyl)-2,5-dihydrothiophene. In continuation of our biological studies of this metabolite, we synthesized the cis and trans isomers of the metabolite. Configurations of these final isomers as well as their precursors are to be determined by 1H, 1H COSY 2D spectra and 1H NOE difference spectroscopy to compare the isomers with the naturally occurring ones.